1. Field of the Invention
The present invention relates to cameras and in particular to cameras having a fixed focal length or zoom lens, and to interchangeable lenses of fixed focal length or zoom lenses which are provided with optimal light protection for a variety of focal lengths by means of an axially adjustable screen.
2. Description of the Prior Art
It is known that sunshades are made to cover short focal lengths, that is, they allow an opening, i.e., field of view, of for example 65.degree.. With long focal length lenses with a light entry angle of for example 7.degree. these fixed sunshades have a limited effect.
It is further known that in order to achieve a light screening effect under for example 65.degree., masks can be placed on the tube-shaped sunshade, which screen the light entry as well as possible. Slots are provided in the sunshade in which a mask can be placed. Such an arrangement is not only complicated to handle, but also inaccurate, since the masks can only be set for fixed focal lengths, and are therefore impractical for zoom lenses or lenses of different focal lengths, since a mask designed for each specific focal length would be needed for each corresponding lens.
It is also known that manually adjustable bellows matt-boxes are used for, for example, super 8 or 16 or 35 mm cinecameras. In such arrangements, the sunshade consists in this case of a collapsible folded bellows which tapers towards the lens, and which will accept masks on its front end. Such bellows units with masks can be adjusted to any focal length and typically have a fixed, rectangular frame on the front of the bellows. In the telephoto position the bellows cannot for practical reasons relating to size be made long enough to provide adequate light protection. Because of this the frame in front of the bellows is constructed to accept an additional mask or masks.
It is furthermore known that an adjustable sunshade can be used where four adjustable doors are attached to the front of the sunshade which can be adjusted in pairs. However, the doors are obviously geometrically limited in their light protection.